Basic support for overlay databases #3949

Job	Run time
Config export (macos-latest, linked)	1m 6s
Config export (ubuntu-latest, linked)	1m 5s
Config export (macos-latest, nightly-latest)	1m 9s
Config export (ubuntu-latest, nightly-latest)	1m 3s
Config export (windows-latest, nightly-latest)	3m 36s
Config export (windows-latest, linked)	3m 33s
	11m 32s

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